Something similar happens with store. I need to set the model when setting new proxy to a memory store, even though it has been set in the store config property. This happened after migrating from PR3 to PR4

This has also been made so you don't need to set the model in the config passed to setProxy().

In the case where you define an operation yourself manually, we require you to specify the Model that the operation is going to be handling. In the refactored data package, Operations take care of handling any type of response (update, destroy, read, create). In order to do this, they need to know which Model they are dealing with. I have updated the documentation to explain this.